1. Field of the Invention
This invention relates to a catalytic process for producing alcohols directly from carbon monoxide and hydrogen. More particularly, the present invention pertains to a tantalum and alkali-containing molybdenum sulfide heterogeneous catalyst and to its use for converting carbon monoxide and hydrogen to alcohols.
2. Description of the Related Art
Almost as old as the Fischer-Tropsch process for making hydrocarbons is the Fischer-Tropsch process for making alcohols. The reaction is carried out by passing a mixture of carbon monoxide and hydrogen over a catalyst for the hydrogenation of the carbon monoxide. A typical review article is R. B. Anderson et al., Industrial and Engineering Chemistry, Vol. 44, No. 10, pp. 2418-2424. This paper lists a number of catalysts containing zinc, copper, chromium, manganese, thorium, iron, occasionally promoted with alkali or other materials for making various alcohols. The authors state that ethyl alcohol is a major constituent, the yield of methanol is usually very small and a tentative summary of factors favoring the production of alcohols is high pressure, low temperature, high space velocity, high recycle ratio and carbon monoxide-rich synthesis gas.
Molybdenum (Mo), tungsten (W) and rhenium (Re) are known catalysts for the Fischer-Tropsch process, Murchison et al. in U.S. Pat. Nos. 4,151,190 and 4,199,522. The references describe some Fischer-Tropsch catalysts but do not teach that the catalyst is useful for making commercially significant quantities of alcohols. These references note that hydrogen sulfide detrimentally affects the activity of the catalyst.
Molybdenum-based catalysts have also been used to catalyze a variety of reactions such as desulfurization, denitrofication and hydrogenation reactions. For example, Stewart U.S. Pat. No. 2,490,488 discloses the use of a molybdenum sulfide catalyst promoted with "minor proportions" of an alkali metal oxide, hydroxide or carbonate to produce liquid hydrocarbons and organic oxygen-containing compounds from carbon monoxide and hydrogen. The preferred amount of the alkali promoter, according to the patent, is about 0.5 to 5 weight percent based on the weight of molybdenum sulfide, or 2-20 mole percent when the promoter is potassium hydroxide. Carbon monoxide and hydrogen are said to be converted to normally liquid hydrocarbons and unspecified organic oxygen-containing compounds utilizing such catalyst.
Frankenburg, U.S. Pat. No. 2,539,414 describes a Fischer-Tropsch process with molybdenum carbide catalysts. It teaches that the catalyst may be used to form oxygenates and at column 3, lines 66-71 teaches that one might get alcohols or hydrocarbons by varying the conditions.
More recently, Kinkade (Union Carbide), European Patent Application No. 84116467.6 (published July 24, 1985, Publ. No. 149,255) discloses that C.sub.1-5 n-alcohols are substantially produced with a catalyst consisting essentially of molybdenum sulfide and an alkali metal compound. The gas hourly space velocity (i.e., GHSV) must be about 3000 hour.sup.-1 or above. Variations in the GHSV, temperature, pressure and alkali metal compound are disclosed to affect the alcohol selectivity.
Quarderer et al. (Dow Chemical), U.S. Pat. No. 4,749,724 discloses that alcohols which boil in the range of motor gasoline are made at good selectivities from syngas with an optionally supported Mo/W/Re and alkali/alkaline earth element catalyst. A potassium-promoted molybdenum sulfide catalyst is most preferred, and when the catalyst is supported, carbon supports are favored. It is preferred to exclude lanthanide and actinide series metal components.
Stevens, U.S. Pat. No. 4,752,622 and Stevens et al., U.S. Pat. No. 4,752,623 (Dow Chemical), disclose catalytic processes for producing alcohols from synthesis gas over a catalyst containing as a first component Mo, W, or Re in free or combined form, and as a second component Co, Ni or Fe in free or combined form, together with an alkali or alkaline earth metal promoter.
Hucul et al., U.S. Pat. No. 4,762,858 (Dow Chemical), employs a reduced catalyst composition which includes as necessary components a catalytic metal of Nb, Ta, Mo, W, Tc, Re or a combination thereof in free or combined form with a cocatalyst of yttrium, a lanthanide or actinide series metal or a combination thereof for converting synthesis gas to predominately C.sub.1 to C.sub.10 oxygenated hydrocarbons and especially C.sub.1 to C.sub.5 mixed alcohols.